Diazotype photoprinting materials



' Patented Nov. 17, 195.3

- =U qm :p* srn rss PATENT OFFICE 2,659,672 nulzo'rrrn rno'roram'rmoMATERIALS Werner Paul Leuch, London, England, asslgnor to Hall HardingLimited, London, England, a corporation of Great Britain and NorthernIreland No Drawing. Application December 21, 1948, Serial N0. 66,579

Claims priority, application 'Great Britain January 9, 1948 "5 Claims.(Cl. 95-6) The present invention relates the production oflight-sensitive layers by means of diazo compounds capable of producingprints in two "or more contrasting colours and in particular in"primarycolours red, yellow or blue, or in comv plementary colours suchas red and green or orange and blue or yellow and violet from one Dfloriginal depending on the composition of the f light-sensitive layer.

, produced by this process may be drawings exe- The originals to berecuted mini: and pencil or in at least two inks or colour washes, whereeach ink or colour wash possesses the property of adsorbing ortransmitting a quantity of light which is substantially diiferent fromthat absorbed orftransmitted by the other ink or colour washes on thedrawing. Also the drawings can be of a kind where one ink transmits nolight at all and the other a definite proportion only of the totalquantity of light transmitted during a given exposure time. makes itpossible to obtain two complementary This colours or two desired primarycolours out of a possible of three, or three colours simultaneproducephotographic prints in two or more contrasting colours frommonochromatic photographic transparencies of different degrees ofdensity.

Other objects of the invention will be mani- .fest from the description.

It has been suggested in the past that prints in'twocolours could beobtained by means of the diazotype process from original drawings of thetype described above by using a light-sensitive layer containing twodiazo compounds, where one diazo would yield one colour with a certaincoupling component and the other diazo a different colour, or where thelight-sensitive layer, composed of the two diazo compounds, could reactwith two coupling components. added to it and thus could produce twodifferent colours on development. Another method attempted for producingtwo colours in one print consisted in using one diazo compound whichcould give difierent shades of colour with one or more couplingcomponents, according to the quantity of diazo compound left on the copyafter exposure to light under a drawing or half-tone positive. All thesemethods have the disadvantagethat they are incapable of producing printsin primary or in complementary colours, since the denser portions of thedrawing or other pattern which is to be reproduced would always containa mixture of the two colours employed. Thus, if. for instance thelight-sensitive layer were arranged in such a manner that one diazocould produce a blue dye and the other diazo a red dye, the denserportions of the drawing would be represented by a mixture of these dyes,which in this case would be violet. The less dense portions could onlybe either blue or red or a mix-,

ture of both with a predominance of one or the other, i.e. both coloursrelated to violet and therefore not contrasting or complementary.

Such colours could not exhibit the good contrasts desired in a technicaldrawing for instance. It will be understood, that our new processproduces positives from positives. The development can be carried out byammonia gas ii the coupling component or components are already presentin the sensitive layer. As an alternative to this case the developmentof the dyestuffs, instead of by means of ammonia gas,

can be eifected by the application of a liquid developer capable ofcausing the components to react with each other. In the case where nocoupling component is added to the light-sensitive solution or layerprior to printing, development can be carried out by the application ofa liquid in which the coupling component or components have beenincorporated together with an alkaline -substance.

The principle on which the present invention operates is that two ormore diazo compounds are used at least one of which (B) is incapable offorming a, dyestufi with the coupling components (C) present in thelight sensitive layer (in the case of layers developed by the ammonia 5gas method) or in the developer (in-the case of moist or semi-drydevelopment), but is capable of coupling with its own decompositionproduct I (D) produced during exposure to light, and that at least oneother diazo compound (A) is used which is capable of coupling with thecoupling as such a manner that suflicient difference in printing outspeeds results between at least two of the diazo compounds used. v

This quantity may, according to they wave length sensitivity of therespective diazo compounds, have to be varied to suit the spectralcomposition of ,the light used for exposure.

For use as diazo compounds (B) which are not capable under the usualconditions of development of forming a dye'stufi with the couplingcomponent already present in the unexposed light-sensitive layer orapplied subsequently with the developer, members of the class of diazoanhydrides or diazo oxides, particularly those of the naphthaleneseries, have been found to be specially advantageous. These generallyare compounds which bleach out in a neutral or acid medium, and areincapable of forming dyestuffs with coupling components of mediumcoupling velocity such for example as 2.3-hydroxynaphthalene-G-sulphonicacid, or the amide of 2.4-resorcylic acid.

The other diazo compounds (A) which are ca-' pable of coupling with thecoupling component (C) may be any of the diazo compounds generally usedin the production of diazotype prints aetacv'a quently, and dye resultson development. with such an arrangement it is therefore possible thatin those portions of a drawing which transmit no light at all, onlydiazo component A can form a dyestufi; in this case blue with couplingcomponent C, while diazo B, not having been affected by light, remainsincapable of forming a'dye. Where both diazo compounds have beenbleached out completely, a White ground is obtained; on the other hand,in the portions where there is still some diazo component A left butwhere diazo component B has started to decompose and form couplingcomponent D, coupling takes place chiefly between coupling component Dand diazo component A to form yet another dyestufi: in the present casethis is a greenish yellow. As at the same time diazo component A alsocouples 'in these portions to a certain extent with coupling componentC, the colour effect can vary, according to the amount of lighttransmitted, from a greenish blue to a yellowish green. The whole colourrange possible with a given light sensitive provided they give thedesired colours with the coupling component employed, and possess therequired sensitiveness to light relative to the diazo compounds (B)employed with them.

The coupling components to be used according to this invention arechosen to give the desired colours with the diazo compounds used and ingeneral are compounds of moderate coupling energy so that they do notcouple with diazo compound denoted as (B) under the conditions used.Coupling components of high coupling energy such as phloroglucinol aretherefore generally not suitable. A large variety of coupling componentsare, however, suitable, examples of such being the 6-mono-sulphonicacids of 2.3- and 3.8-dihydroxyn-aphthalenes, the amide of 2.4-resorcylic acid, resorcinolpropyl ether, m-hydroxyphenyl urea and themonoglycol ether of pyrocatechol.

The method of carrying out this process is exemplified by the followingdescription but of course the invention is in no way limited to thecolours indicated.

Two diazo compounds A and B are brought onto a suitable base such aspaper, together with a coupling component C. Diazo component A iscapable of forming a blue dyestufi with coupling component C under givenconditions. Diazo component B however is incapable of forming a dyestuffwith coupling component C under the same conditions. On the other handdiazo component B forms, during exposure to light, a coupling componentD with which it is capable of forming a red dyestufi in those portionsof the copy where not all the diazo component has been destroyed by thelight. Where this decomposititon of B with consequent formation ofcoupling component D is about 50% of the total of B in the layer the reddye is most intense. It must be understood that for the purpose of thisprocess the two diazo compounds A and B either must possess diiferentsensitiveness to the light of a given light source or must be mixed insuch proportions in the sensitizing solution, that one diazo componentprints out faster than the other. The proportions have to be arranged sothat for instance there is still a considerable amount of diazocomponent B left in some of those portions where A has already beencompletely destroyed by the action of light. In those portions,conselayer of the described type can best be studied by exposing itunder a grey wedge photometer used for sensitometry. with a definitewedge constant. We have found that a very' suitable wedge is one wherethe wedge constant is equal to 1.414 (V5); to this sensitometer we add,for purposes of comparison a solid black which transmits no light. Whenthe correct exposure for a given light sensitive layer has beendetermined under an arc lamp, the developed print will exhibit thefollowing colours: from white, where both the diazo compounds have beencompletely bleached out, via pale red to intense red (where some diazocomponent B is left to the maximum depth where about half the diazocomponent B has been converted to the coupling component D but where nodiazo component A is left), to yellowish green which gradually changes,up the scale to green and bluish-green (where diazo component A existsin increasing quantity and coupling component D diminishesproportionately to the amount of light received by diazo component B)and finally to greenish-blue and pure blue respectively (i. e. fromwhere only minute quantities of coupling component D have been formed towhere no coupling component D is present). An Eder- Hecht sensitometercan be used equally well for this purpose of testing the colours. Ifinstead of these types of wedges 'one uses a Wratten wedge utilised inthree-colour half-tone printing, the colour changes on the print aremore abrupt, i. e. they show up with fewer intermediate steps of shades,and practically only yield bright red, green and blue-grey, with pureblue under solid black. portions.

From the above description it can easily be visualised that a technicaldrawing, where certain portions are executed in black ink, or in anyother ink which does not transmit light, and other portions in pencilwhich allows a certain amount of light to be transmitted, can bereproduced by means of the described type of lightsensitive layer insuch a way that the two drawingmediums show up on the copy in twoprimary colours, such as blue and red and that it is possible byutilising a second pencil giving a deeper shade of grey, i. e.transmitting less light than the first pencil, to add a third colour,such as green in the present case. In the place of pencil one can useinks, either coloured or grey, with aesaeva proportions of diazocomponent A and diazo com- I ponent B in the layer. It instead oi twoprimary colours it is desired-to obtain copies in complementary colours,

ponent E. which possesses approximately the this can for instance beachieved by adding yet another coupling com-' same coupling energy ascoupling component C and which produces a yellow dye with diazocomponent A and, of course, no colour with diazo component B. In thiscase the image is composed chiefly of green and'red dyes. When theoriginal to be reproduced is a suitable photographic halftone positive,the colours obtained correspond to the various densities of the originalin the same manner as on the wedge sensitometer.

A suitable light-sensitive layer of the type described contains alsostabilisers which ensure good keeping qualities of the material beforeprinting and ingredients which counteract the yellowing of the copyafter it has been made. In the case of moist development of the print,the anti-yellowing agents can be incorporated in the developer, but thelight-sensitive layer and developer must be compounded in such a manner'that'no excess alkali is left on the paper after completed development,if good stability of the prints is desired.

The following examples serve to illustrate the manner in which the newlight-sensitive layers may be produced, but the invention is of coursein no way limited to these examples.

EXAMPLE 1 (Solution 1 ,for blue) In 150 cc. water dissolve 12 gr.tartaric acid 10 gr. thiourea 5.1 gr. zinc chloride double salt ofl-N-ethyl-hydroxy-ethylamino benzene-i-diazonium chloride (Diazocompound A) 4.5 gr. 2.3 dihydroxynaphthalene 6 sulphonic acid (Couplingcomponent C) 1o gr. zinc chloride 3 cc. diethylene glycol or glycerine(Solution 2 for red) 150 cc. water 12 gr. tartaric acid 10 gr. thiourea6 gr. zinc chloride 3 cc. diethylene glycol 3.6 gr. sodium salt of thediazoanhydride of 2- amino-l-naphthol-B-sulphonic acid (Diazo compoundB) By mixing these two solutions in equal proportions, and coating themon a suitable base such as paper in known manner, and then exposingtothe light of an arc lamp the light-sensitive layer thus obtained, undera drawing such as has been described above, copies are obtained whichafter development by means of ammonia gas show the reproduction asfollows: Dense ink lines are reproduced in blue, pencil lines in brightred in the case of lines of medium density and green in the 6 denserpencil lines or shadings. It the exposure is made under a high pressuremercury vapour tube, the red colour is replaced chiefly by yellow andorange on account of the fact that diazo compound A employed in thisexample is relative to diazo compound B, less sensitive to this li htthan to the light of the arc lamp. The'same applies when exposure ismade in full sunligh". colours reach their full brightness only afterallthe ammonia gas has left the paper. Also the prints, when freshlydeveloped, shouldnot be exposed to strong daylight or other stronglyactinic light sources until the ammonia gas has evaporated from theprints, if pure blue shades are desired. In order to obtain the bestresults it is essential that the apparatus used for making the copiesprovides good contact between the original and the light-sensitivematerial during printing.

If a further coupling component, such as acetoacet-o-toluidide,isadded'to Solution 1 and the quantity of 2.3 dihydroxynaphthalene 6sulphonic acid is correspondingly diminished, green colours are obtainedin place of blue beside the red. If the diazo compound in Solution 1 isreplaced by an equivalent quantity of the zinc chloride double salt of5-diethylaminotoluene-2- diazonium chloride, the blue shades obtainedare more greenish. If instead of the colours 'described it is desired toobtain copies with blue colours for the dense portions of the originaland the complementary orange colour for the lighter portions, onereplaces the diazo anhydride used in Solution 2.by means of the diazoanhydride of 2 amino l naphthol-i-sulphonic acid. These colours can alsobe replaced by violet for the dense portions and yellow for the lightportions by using a modified form of Solution 1 in which the2.3-dihydroxynaphthalene-B-sulphonic acid is replaced by2.8-dihydroxynaphthalene-6-sulphonic acid and a modified form ofSolution 2 in which the diazo anhydride mentioned is replaced by thediazo anhydride of l-amino-2- naphtholl-sulphonic acid.

EXAMPLE 2 In this example the diazo compound designated as diazocompound A in Example 1 is replaced by a mixture of 3 grams of the zincchloride double salt of 3-chloro l diethyl amino benzene-4- oliazoniumchoride and 4 grams of the zinc chloride double salt oit-diethylamino-l-toluene-3- diazonium chloride. By working in the mannerdescribed in Example 1 it will be found that the light tones arereproduced in red, the medium tones chiefly in yellow and the darkertones in stance, in an original ink drawing, alterations.

may be shown in pencil and it may be desired.

in the photograph to emphasize these alterations. so that they stand outmore prominently than the original drawing. By a suitable choice ofcomponent materials and of exposure, the present. process enables thedark lines of the original, drawing to be reproduced in alight colourand. the lighter lines of the drawing to be reproduced.

in a contrasting darker colour.

The-

7 EXAMPIE 3 A solution is prepared from 100 cc. of water in which aredissolved 6 gr. tartaric acid gr. thiourea 5 gr. zinc chloride 2 cc.polyglycol 3 gr. sodium salt of the diazoanhydride 01' 1-amino-2-naphthol-3.6 disulphonic acid 8 gr. zinc chloride double salt of4-diethylaminol-diazonium chloride 1 gr. monoglycolether o1 pyrocatecholThis solution when coated on paper and exposed and developed in themanner described in Example 1 gives a print in which the pencil lines ofthe drawing are shown in violet-blue, whereas the darker ink lines 01'the drawing are shown in bright yellow. If, however, the diazo anhydrideused in this example is replaced by the diazo anhydride used in Example1 then the pencil lines of the original drawing are reproduced inbrilliant red and the ink lines of the gas method) or in the developer(in the case of moist or semi-dry development) but is capable ofcoupling with its own decomposition product;

and where at least one other diazo compound is used which is capable ofcoupling with the coupling component introduced into the light-sensitivesolution or applied with the developer, and the respective quantities ofthe diazo compounds used in the sensitive solution are arranged in sucha manner that sufilcient difference in printing speeds results betweenat least two of the diazo compounds used.

What I claim and desire to secure by Letters Patent is:

1. A light-sensitive layer for the production of a multi-colored'diazotype photographic print which contains a coupling component, C, andtwo diazo compounds at least one, B, of which is a .member of the groupconsisting of diazo anhydrides and diazo oxides which diazo compound isincapable of forming a dyestufi with said coupling component C butiscapable of coupling with the decomposition product, D, produced from Bby the action of light and another one, A. of which is capable ofcoupling with said coupling component C, the relative quantities of thesaid diazo compounds A and B being such that there is a substantialdiflerence in their printing out speeds.

2. A light-sensitive layer according to claim 1 in which the diazocompounds present in the light-sensitive layer are the zinc chloridedouble salt of 1-N-ethyl-hydroxy-ethylamino-benzene- 4-diazoniumchloride and the sodium salt of the diazo anhydride 0:1-amino-2-naphtho1-4-sulphonic acid and in which the coupling componentis 2,8-dihydroxynaphthalene-6-sulphonic acid.

3. A light-sensitive layer according to claim 1 in which the diazocompounds present in the light-sensitive layer are the zinc chloridedouble salt Of 4-diethylamino-iediazonium chloride and the sodium saltor the diazo anhydride or 1- amino-2-naphthol-3.6-disulphonic acid andthe coupling component is the mono-glycolether o1 pyrocatechol.

4. A light-sensitive layer for the production of a multi-coloreddiazotype photographic print. which contains a coupling component, C,and at least two diazo compounds one, B, of which is a member of thegroup consisting of diazo anhydrides and diazo oxides which diazocompound is incapable of forming a dyestufl with said coupling componentC but is capable of coupling with the decomposition product, D,producedtrom B by the action 01' light. and another one, A, of which iscapable of coupling with said coupling component C, the relativequantities of the said diazo compounds A and B being such that there isa substantial difference in their printing out speeds, thelight-sensitive layer being further characterized in that the diazocompounds present therein are the zinc chloride double salt of 1- Nethyl hydroxy ethylamino benzene 4- diazonium chloride and the sodiumsalt or the diazo anhydride or 2-amino-1-naphthol-5-sulphonic acid andin that the coupling component is 2.3-dihydroxynaphthalene-s-sulphonicacid.

5. A process for the production of a multicolored diazotype print bycoating at least two light-sensitive diazo compounds on a support andexposing the coated material behind a transparent design to the actionof actinic light and then developing the print by coupling the diazocompounds with coupling components characterized in that thelight-sensitive layer contains a coupling component, C, in that one, B,or the diazo compounds is a member of the group consisting ofdiazoanhydrides and diazo oxides which diazo compound is incapable offorming a dyestuif with coupling component C but is capable of couplingwith the decomposition product, D, produced from said diazo compound 3by the action of light thereon, in that a second one, A, of the diazocompounds is capable of coupling with said coupling component C, therelative quantities of A and B being such that, under the conditions ofexposure to the light source employed, there is a substantial diiferencein their printing out speeds, and in that after exposure to light theprint is developed by treatment with an alkaline substance.

WERNER PAUL Lnucn.

References Cited in the file 01 this patent UNITED STATES PATENTS OTHERREFERENCES Spencer: Photographic Applications of Diazo Compounds," ThePhotographic Journal, Dec. 1928, pages 490 to 496, page 494 cited.

1. A LIGHT-SENSITIVE LAYER FOR THE PRODUCTION OF A MULTI-COLOREDDIAZOTYPE PHOTOGRAPHIC PRINT WHICH CONTAINS A COUPLING COMPONENT, C, ANDTWO DIAZO COMPOUNDS AT LEAST ONE, B, OF WHICH IS A MEMBER OF THE GROUPCONSISTING OF DIAZO ANHYDRIDES AND DIAZO OXIDES WHICH DIAZO COMPOUND ISINCAPABLE OF FORMING A DYESTUFF WITH SAID COUPLING COMPONENT C BUT ISCAPABLE OF COUPLING WITH THE DECOMPOSITION PRODUCT, D, PRODUCED FROM BBY THE REACTION OF LIGHT AND OTHER ONE, A OF WHICH IS CAPABLE OFCOUPLING WITH SAID COUPLING COMPONENT C, THE RELATIVE QUANTITIES OF THESAID DIAZO COMPOUNDS A AND B BEING SUCH THAT THERE IS A SUBSTANTIALDIFFERENCE IN THEIR PRINTING OUT SPEEDS.